Cell pillar structures and integrated flows

ABSTRACT

Various embodiments comprise apparatuses and methods, such as a memory stack having a continuous cell pillar. In various embodiments, the apparatus includes a source material, a buffer material, a select gate drain (SGD), and a memory stack arranged between the source material and the SGD. The memory stack comprises alternating levels of conductor materials and dielectric materials. A continuous channel-fill material forms a cell pillar that is continuous from the source material to at least a level corresponding to the SGD.

PRIORITY APPLICATION

This application is a divisional of U.S. application Ser. No.15/056,548, filed Feb. 29, 2016, which is continuation of U.S.application Ser. No. 13/838,579, filed Mar. 15, 2013, now issued as U.S.Pat. No. 9,276,011, all of which are incorporated herein by reference intheir entirety.

BACKGROUND

Computers and other electronic systems, for example, digitaltelevisions, digital cameras, and cellular phones, often have one ormore memory and other devices to store information. Increasingly, memoryand other devices are being reduced in size to achieve a higher densityof storage capacity and/or a higher density of functionality.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A through FIG. 1H show various portions of a fabrication processto form strings of memory cells, according to an embodiment;

FIG. 2A and FIG. 2B show various portions of a fabrication process toform strings of memory cells, according to an embodiment; and

FIG. 3 is a block diagram of a system embodiment, including a memorydevice according to various embodiments described herein.

DETAILED DESCRIPTION

The description that follows includes illustrative apparatuses(circuitry, devices, structures, systems, and the like) and methods(e.g., processes, protocols, sequences, techniques, and technologies)that embody the disclosed subject matter. In the following description,for purposes of explanation, numerous specific details are set forth inorder to provide an understanding of various embodiments of the subjectmatter. After reading this disclosure, it will be evident to person ofordinary skill in the art however, that various embodiments of thesubject matter may be practiced without these specific details. Further,well-known apparatuses, methods, and operations have not been shown indetail so as not to obscure the description of various embodiments.

As used herein, the term “or” may be construed in an inclusive orexclusive sense. Additionally, although various embodiments discussedbelow focus on a three-dimensional (3D) NAND memory device, theembodiments are readily applicable to a number of other electronicdevices. Consequently, the described embodiments are merely given forclarity in disclosure, and thus, are not limited to NAND memory devicesor even to memory devices in general.

Generally, a 3D electronic device may be considered to be a deviceformed by a process that combines multiple levels of electronic devices(e.g., one device formed over another) using planar formations (e.g.,multiple devices on a single level). Since multiple levels in 3D devicesmay use approximately the same area on a substrate, an overall densityof devices (e.g., memory devices) can be increased in relation to thenumber of levels. Generally discussed herein are three-dimensional (3D)memories, memory cells, and methods of making and using the same. In oneor more embodiments, a 3D vertical memory can include a memory stacksharing a common cell-pillar. A memory stack can include a stack of atleast two memory cells and a dielectric between adjacent memory cells,where each memory cell includes a control gate (CG) and a charge storagestructure, such as a floating gate (FG) or charge trap (CT), configuredto store electrons or holes accumulated thereon. Information isrepresented by the amount of electrons or holes stored by the cell.

The methods and apparatuses discussed herein can be extended to NORdevices, microcontroller devices, other memory types, general purposelogic, and a host of other apparatuses. Various 3D devices includingrepeating devices (e.g., SRAM), transistors, standard CMOS logic, and soon may all benefit from application of the fabrication processesdisclosed herein.

Prior art devices allowed a continuous cell pillar only from the sourcethrough the memory cells. However, a separate photolithography stepcaused a shoulder to be formed when the drain-side select gate (SGD) waslater formed over the memory cells. The shoulder caused a pinch-point,thereby reducing current flow from source to a bitline formed over theSGD.

In various embodiments disclosed herein, a continuous cell pillar isformed substantially through all levels of the 3D devices. Therefore,the cell pillar (e.g., channel) is a continuous formation from at leastthe source-side select gate (SGS) to SGD. The continuous cell pillarimproves current flow over prior art devices by, for example, removingpolysilicon-to-polysilicon channel interfaces in between the SGD and thecell pillar and also between the SGS and the cell pillar, as well aseliminating structural offsets within the cell pillar formation of theprior art that limits the current path. Further, the disclosed subjectmatter reduces process steps and costs. In various embodiments, thechannel-to-source interface may be defined by integrating a bufferpolysilicon to a transition metal/semiconductor source (e.g., WSi_(x))source or an etch stop formed using a high-dielectric constant (high-k)material.

Consequently, the disclosed subject matter eliminates certainphotolithographic and registration operations and eliminates particularinterface and critical dimension/registration offsets as found in theprior art in between, for example, the SGD, the SGS, and thecell-pillar. Further, the disclosed subject matter eliminates or reducesthe number of chemical-mechanical planarization (CMP) steps for both theSGS and the cell pillar, reducing SG-to top and bottom access line(e.g., wordline) distances by approximately 50%. Further, an N+ bufferpolysilicon may be utilized between the WSi_(x) source and the channelmaterial forming an ohmic contact.

FIG. 1A through FIG. 1H show various portions of a fabrication processto form strings of memory cells, according to an embodiment. Asdiscussed above, the techniques and fabrication processes describedherein can be extended to a number of different apparatuses (e.g., inaddition to memory devices) to be fabricated using various processes,including, for example, a three-dimensional process. However,fabrication of a NAND memory device 100 will be described below toretain clarity and consistency in the discussions that follow.

In FIG. 1A, initial formation of the NAND memory device includes forminga source material 101 having levels of various materials formedthereover including various dielectric materials and semiconductormaterials as discussed in more detail below. Each of these and othermaterials described herein may be applied, deposited, or otherwiseformed according to techniques and methods known independently in theart. The techniques and methods can include one or more depositionactivities, such as chemical vapor deposition (CVD), atomic leveldeposition (ALD), physical vapor deposition (PVD), or other techniques.Forming multiple materials in various levels may be accomplished viastacked deposition operations.

Although the process acts and operations described herein may refer toparticular conductor, semiconductor, or dielectric materials, such assilicon, silicon dioxide, silicon nitride, or others, a person ofordinary skill in the art and familiar with this disclosure willrecognize that other conductor, semiconductor, and dielectric materialsmay be substituted and still be within a scope of the disclosed subjectmatter. Thus, the material choices and selections presented are merelyprovided as an aid in understanding one example of a fabricationprocess.

For example, various types of semiconductor materials, (e.g.,single-crystal or amorphous silicon, germanium, other elementalsemiconductor materials, compound semiconductor materials, etc.) may beused as an alternative for or in conjunction with other types ofsemiconductor material. Additionally, various types of dielectricmaterials, such as tantalum pentoxide (Ta₂O₅), silicon nitride(Si_(x)N_(y)), aluminum oxide (Al₂O₃), hafnium oxide (HfO₂), and avariety of other organic or inorganic dielectric materials, may be usedas an alternative to or in conjunction with others of the materialsdescribed. Also, various other combinations of materials may also besubstituted or included. For example, in certain applications, describedsemiconductor materials may be substituted with conductor materialsincluding, for example, silver (Ag), copper (Cu), Aluminum (Al), zinc(Zn), platinum (Pt), tungsten (W), titanium (Ti), or tantalum (Ta).

Further, various formation, process, and other discussions that followmay refer to one material placed, for example, “over” or “above” anothermaterial. Such descriptors are relative terms only and obviously dependupon an exact orientation of any resulting device. However, a person ofordinary skill in the art will readily understand the context of suchrelative terms upon reading and understanding the disclosure providedherein in conjunction with the respective drawings.

With continuing reference to FIG. 1A, the source material 101 caninclude, for example, a conductively doped poly-silicon material or aconductively doped region of a semiconductor substrate. As referred toherein, a semiconductor substrate can be any of various types ofsubstrates used in the semiconductor and allied industries, such assilicon wafers, other elemental semiconductor wafers, compoundsemiconductor wafers, thin film head assemblies,polyethylene-terephthalate (PET) films deposited or otherwise formedwith a semiconducting material layer (followed by an annealing activity,such as excimer laser annealing (ELA) in some embodiments), as well asnumerous other types of substrates known independently in the art. Also,in some embodiments, the source material 101 may be formed over anon-semiconductor material (e.g., quartz, ceramic, etc.), or vice-versa.Other embodiments for the source material 101 are discussed, below, withreference to FIG. 2A.

A buffer material 103A is formed over the source material 101 followedby an etch stop 105A. The buffer material 103A may be selected to be aconductive material, for example, a doped polysilicon. In a specificembodiment, the buffer material 103A may be doped as an n-typepolysilicon. In various embodiments, the etch stop 105A may comprise ahigh dielectric constant (high-κ) material such as aluminum oxide(Al₂O₃) or other high dielectric constant oxides. In other embodiments,one or more high-κ materials including, for example, hafnium silicate(HfSiO₄), zirconium silicate (ZrSiO₄), hafnium dioxide (HfO₂), andzirconium dioxide (ZrO₂) may be selected for the etch stop 105A.Generally, a high dielectric constant material may be considered as anymaterial having a dielectric constant equal or greater than thedielectric constant of silicon dioxide. The dielectric constant forsilicon dioxide is approximately 3.9.

Formation of the etch stop 105A is followed by formation of asource-side select gate (SGS) structure including a first dielectricmaterial 107 (e.g., silicon dioxide, SiO₂), a semiconductor material 109(e.g., conductively doped poly-silicon), and a second dielectricmaterial 111 (e.g., SiO₂).

The first dielectric material 107 and the second dielectric material 111may be of the same or different materials. Also, the first dielectricmaterial 107 and the second dielectric material 111 may be formed fromthe same material but by different methods. For example, the firstdielectric material 107 may comprise a thermally-grown silicon dioxidematerial and the second dielectric material 111 may comprise a depositedsilicon dioxide material (or vice versa). As a person of ordinary skillin the art understands, there are certain optical, electrical, and otherdifferences between these two types of formed silicon dioxides. Thus,the material choices and selections presented are merely provided as anaid in understanding one example of a fabrication process.

Depending upon an etchant used in later process steps, the semiconductormaterial 109 may be selected to be a p-type polysilicon (e.g., dopedwith boron). For example, as discussed in more detail below, asubsequent etch-back process step may employ tetramethyl-ammoniumhydroxide (TMAH) as an etchant. TMAH selectively etches n-type andundoped polysilicon but only very slowly etches p-type polysilicon.Selecting the semiconductor material 109 to be p-type polysiliconreduces the amount of the semiconductor material 109 that is etchedduring a subsequent TMAH etch process.

Still continuing with FIG. 1A, a number of alternating materials can beformed over the second dielectric material 111. In various embodiments,forming the alternating materials begins a fabrication process to formvertical memory cells (e.g., a memory array). In other embodiments,forming the alternating materials begins a fabrication process to formother active device types. The number of alternating materials can beselected depending upon the application and device type desired.

The alternating materials comprise a number of additional dielectricmaterials 111 and a number of conductor materials 113A. Each of thelevels of the dielectric material 111 is separated from a respectiveadjacent one of the levels of the dielectric material 111 by at least arespective one of the levels of the conductor material 113A.

Each of the additional dielectric materials 111 may comprise silicondioxide or a number of other dielectric materials. In variousembodiments, one or more of the additional dielectric materials 111 maycomprise a solid electrolyte. The solid electrolyte may comprise achalcogenide, for example, silver-doped germanium selenide (Ag—GeSe),silver-doped germanium sulfide (Ag—GeS₂), copper-doped germanium sulfide(Cu—GeS₂), or copper telluride (CuTe_(x)); or an oxide, e.g. atransition-metal oxide (e.g., ZrO_(x)), a semiconductor oxide (e.g.,SiO_(x)), a rare earth oxide (e.g., YbO_(x)), another metal oxide (e.g.,Al_(y)O_(x)), or combinations thereof, (e.g., ZrSiO_(x)). In theseembodiments, one or more of the memory cells in the memory array maycomprise resistance change memory (RCM) cells. The RCM cells include thetype of cell known as a conductive-bridging RAM (CBRAM) memory cell. Anoperation of the RCM is based on a voltage-driven ionic migration andelectrochemical deposition of metal ions within a solid electrolyte.

The conductor materials 113A may comprise conductively dopedpoly-silicon or a number of other conductor or semiconductor materials.Although each of the dielectric materials 111 and the conductormaterials 113A may be construed as being comprised of the same materialon each level, respectively, various levels may comprise differentmaterials. For example, a first level of the dielectric material 111 maycomprise silicon dioxide while a later-formed second level of thedielectric material 111 may comprise tantalum pentoxide. Similarly, afirst level of the conductor material 113A may comprise conductivelydoped poly-silicon while a later-formed second level of the conductormaterial 113A may comprise conductively-doped germanium, a dopedcompound-semiconductor material, or a metallic-ion donor such as silver.In a specific exemplary embodiment, the conductor material 113A is an-type polysilicon.

A drain-side select gate (SGD) comprising a semiconductor material 115is formed over the alternating materials having the number of additionaldielectric materials 111 and the number of conductor materials 113A. Aswith the semiconductor material 109 and depending upon an etchant usedin later process steps, the semiconductor material 115 may be selectedto be a p-type polysilicon (e.g., polysilicon doped with boron or otherelements from Group 13 of the periodic table). For example, as discussedin more detail below, a subsequent etch-back process step may employTMAH as an etchant. TMAH selectively etches n-type and undopedpolysilicon but only very slowly etches p-type polysilicon. In otherembodiments, the semiconductor material 115 may be used for other typesof active semiconductor switching devices.

A chemical-mechanical planarization (CMP) etch-stop material 117 may beformed over the semiconductor material 115 and comprises a relativelyhard material to act as a stopping point for subsequent CMP processes.The CMP etch-stop material 117 may comprise one or more materialsincluding dielectric materials such as various oxides, oxynitrides, ornitrides.

A cap material 119 is formed over the CMP etch-stop material 117 andprovides protection for the underlying materials during subsequentprocess steps. The cap material 119 may comprise one more materialsincluding oxides, nitrides, high-κ dielectric materials, polysilicon,and other materials independently known in the art. A hard-mask material121 and a photoresist level 123 allow initial formation of a partialvia, or shallow trench, for a subsequent pillar etch operation,discussed below. The hard-mask material 121 may comprise, for example,carbon with a dielectric anti-reflective coating. The cap material 119and the hard-mask material 121 may be considered to be sacrificialmaterials provided to aid in subsequent formation steps. After thehard-mask material 121 is patterned and opened for the subsequent pillaretch operation, the photoresist level 123 may be removed.

Table I, below, shows a specific exemplary embodiment of variousdimensions (e.g., thicknesses) of the various materials discussed above.A person of ordinary skill in the art will recognize that dimensions andrelative dimensional ratios, other than those shown, may function forvarious device types. However, the dimensions given are provided simplyas an aid in understanding the various embodiments discussed herein andshould not be considered as the only workable, or even preferable,dimensions.

TABLE I Material Level Element Number Dimension (nm) Source Material 101 50 to 200 Buffer Material  103A 30 Etch Stop  105A 20 to 50 FirstDielectric Material 107 20 to 50 Semiconductor Material 109 100 to 300Dielectric Material 111 20 Conductor Material  113A 30 SemiconductorMaterial 115 100 to 300 CMP Etch-Stop Material 117 10 to 20 Cap Material119 200 

Referring now to FIG. 1B, formation of the NAND memory device 100continues with formation of a pillar opening 110. The pillar opening 110is performed in preparation for a subsequent channel formation,discussed below, and may be etched or otherwise formed to be a partialvia of various shapes or a trench. For example, in various embodiments,the pillar opening 110 is a trench. In other embodiments, the pillaropening 110 may be comprised of geometries other than a trench. However,for ease in understanding fabrication operations of the disclosedsubject matter discussed herein, the pillar opening 110 can beconsidered to be an opening (e.g., an aperture) formed at leastpartially through the various materials discussed above.

In a specific embodiment, the pillar opening 110 can be formed by ananisotropic dry etch process (e.g., reactive ion etch (RIE) or plasmaetch). In other embodiments, depending upon materials selected, thepillar opening 110 may be formed by one or more various types ofchemical etchants (e.g., such as potassium hydroxide (KOH) ortetramethyl ammonium hydroxide (TMAH)), mechanical techniques, othertypes of ion milling, or laser ablation techniques. Related industriessuch as those involved in constructing micro-electrical mechanicalsystems (MEMS) devices may independently supply techniques for stillfurther means to form the pillar opening 110.

The etch stop 105A of FIG. 1A allows the pillar opening 110 to be formedin a single step, unlike the prior art that requires a separateformation and etch of the SGD pillar as discussed above. As disclosedherein, formation of the pillar opening 110 provides a single continuousopening for later formation of channel material. As shown in FIG. 1B,formation of the pillar opening 110 may etch partially into the etchstop 105A (FIG. 1A), forming an etch stop 105B that is at leastpartially-opened. In a specific exemplary embodiment, an aspect ratio ofthe overall height of the pillar opening 110 to the width of the openingmay be up to 35:1 or more.

In FIG. 1C, the hard-mask material 121 may be removed. The conductormaterials 113A (FIG. 1A and FIG. 1B) are recessed during a control-gaterecess operation by etching or otherwise have portions removed laterally(forming a recess away from the sidewall of the pillar opening 110). Thecontrol-gate recess operation forms a number of control gates 113B fromthe conductor material 113A of FIG. 1A, thereby forming a recessedpillar opening 120. An isotropic etchant with a relatively highselectivity ratio may be used to form the recesses of the control gates113B.

In a specific embodiment, TMAH may be used to form the recesses. TMAHhas approximately a 6:1 selectivity ratio based on its ability to etchn-type polysilicon approximately six times faster than p-typepolysilicon or dielectric materials. Consequently, due to the highselectivity ratio of TMAH, the n-type polysilicon of the control gates113B is laterally etched faster than the p-type polysilicon of thesemiconductor material 109, 115 or the dielectric materials 107, 111,119. Although the recessed pillar opening 120 is described as beingperformed using TMAH as an isotropic etch, a skilled artisan willrecognize that other types of chemical and/or mechanical etch orformation processes may be used with an appropriate material selection.For example, other isotropic etchants may also be employed such as ahydrofluoric/nitric/acetic (HNA) acid chemical etchant.

During the TMAH etch operation and potential subsequent cleaning steps,the etch stop 105B is opened to the underlying buffer material 103A(FIG. 1B) that may be at least partially etched to form buffer material103B (FIG. 1C). Since the buffer material 103B is a conductive material(e.g., n-type polysilicon), the recessed pillar opening 120 allows asubsequently formed channel to be in electrical communication with thesource material 101.

With reference now to FIG. 1D, an inter-polysilicon dielectric (IPD)material 125A, (e.g., a charge blocking dielectric (CBD) material), isformed on the sidewalls of the recessed pillar opening 120 of FIG. 1C,followed by a charge-storage material 127A being formed adjacent to theIPD material 125A. As indicated in FIG. 1D, the IPD material 125A andthe charge-storage material 127A are primarily or entirely formed onopposing faces of the recessed pillar opening 120 (FIG. 1C). Theformation of the IPD material 125A and the charge-storage material 127Aresults in a pillar opening 130 that is temporarily reduced in size fromthe various pillar openings discussed above.

The IPD material 125A may comprise one or more of the various dielectricmaterials discussed herein, including various high-κ dielectricmaterials. In various embodiments, the IPD material 125A may comprise anoxide-nitride-oxide (ONO) material. The charge-storage material 127A maycomprise one or more of the semiconductor materials discussed herein.For example, in various embodiments, the charge-storage material 127Acomprises polysilicon. In various embodiments, the charge-storagematerial 127A comprises silicon nitride (e.g., Si₃N₄).

In FIG. 1E, an etch process substantially removes excess amounts of theIPD material 125A and charge-storage material 127A from sidewalls andbottom of the pillar opening 130 of FIG. 1D, forming a cleared pillaropening 140 and leaving a number of charge-storage structures 127Belectrically separated from at least proximate (e.g., adjacent) ones ofthe control gates 113B by a partially surrounding IPD material 125B.Techniques to remove the materials from the pillar opening 130 are knownindependently in the art.

For example, the charge-storage material 127A may be at least partiallyremoved from the pillar opening 130, and remaining portions of thecharge-storage structures 127B may be left in the recesses. In variousembodiments, the charge-storage structures 127B may be used to formfloating gates or charge traps. Portions of the charge-storage material127A can be removed using a Certas™ (e.g., a vapor ammonia), an ammoniumfluoride and nitric acid mix (NH4F—HNO3), an ozone (O3) or hydrofluoricacid (HF) mix or cycle (e.g., exposed surfaces can be exposed to ozoneto create oxide (e.g., oxidize) the surface and the oxidized surface canbe exposed to hydrofluoric acid to remove the oxide), hydrofluoric acidand nitric acid mix (HF—HNO3), hydrofluoric acid and hydrogen peroxidemix (HF—H2O2) or a TMAH process. The process used to remove portions ofthe charge-storage material 127A can be selected as a function of thedoping of the charge-storage material 127A. For example, if thecharge-storage material 127A is n-type polysilicon, the TMAH process canbe used to remove the portions of the charge-storage material 127A.

In FIG. 1F, a tunneling material 129 is formed on sidewalls and bottomwithin the cleared pillar opening 140 (FIG. 1E), followed by formationof a sacrificial liner 131A. The tunneling material 129 may comprise oneor more of the dielectric materials discussed herein. The sacrificialliner 131A protects the tunneling material 129 from a subsequentpunch-etch operation.

The tunneling material 129 may be formed from a number of dielectricmaterials discussed herein that allow for Fowler-Nordheim tunneling ofelectrons or direct tunneling of holes or other injection mechanisms.For example, in various embodiments, the tunneling material 129comprises deposited and/or thermally-grown silicon dioxide.

In various embodiments, the sacrificial liner 131A may comprisepolysilicon. In other embodiments, if the tunneling material is athermally-grown silicon dioxide, the sacrificial liner 131A may comprisea deposited silicon dioxide that can be chemically removed with abuffered-oxide etchant (BOE), such as such as a combination of ammoniumfluoride (NH₄F) and hydrofluoric acid (HF) that readily etches materialssuch as silicon dioxide, but has little affect on materials such aspolysilicon. In other embodiments, the sacrificial liner 131A maycomprise the same material as the conductor material 113A, and isremoved using an isotropic etchant, such as a directional RIE or plasmaetch. In still other embodiments, the sacrificial liner 131A maycomprise another dielectric such as borophosphosilicate glass (BPSG)supplied from a tetraethoxysilane (TEOS) source. In still otherembodiments, the sacrificial liner 131A may comprise a solvent-basedliquid that is applied to substrates using a spin-coat process, such asphotoresist. The use and application of these various materials will beunderstood by a person of ordinary skill in the art upon reading andunderstanding the disclosure provided herein.

Referring now to FIG. 1G, sacrificial liner portions 131B is formed by,for example, a punch-etch operation that clears at least the bottomportion of the sacrificial liner 131A (FIG. 1F) and the tunnelingmaterial 129 opening the pillar opening to the source material 101. Thecap material 119 may optionally be removed by the punch-etch operation.

In FIG. 1H, any remaining sacrificial liner portions 131B (FIG. 1G) maybe removed and the cleared pillar opening 140 may be filled with achannel-fill material 133 comprising, for example, poly-silicon or othersemiconductor material. In various embodiments, the channel-fillmaterial 133 may comprise any one or more of the elemental or compoundsemiconductor materials discussed above. The channel-fill material 133may also comprise any of a number of types of single-crystal oramorphous semiconductor materials. For example, the channel-fillmaterial 133 may comprise an epitaxial deposition of silicon, otherelemental semiconductor, or compound semiconductor. In other examples,the channel-fill material 133 may comprise a polysilicon material (e.g.,a conductively doped polysilicon material) formed by, for example,thermal decomposition or pyrolysis of silane such as a low-pressurechemical vapor deposition (LPCVD) process. Other techniques knownindependently in the art, such as DC sputtering, followed by apost-anneal activity in some embodiments, may also be utilized.

Although not shown explicitly in FIG. 1H, the cap material 119 may beremoved (e.g., if it has not already been removed in a prior process(e.g., an etch step) before the process associated with FIG. 1H). Thechannel-fill material 133 may then be planarized (e.g., using achemical-mechanical planarization (CMP) technique) so that the uppersurface of the channel-fill material 133 is substantially coplanar withan upper surface of the CMP etch-stop material 117.

With reference now to FIG. 2A and FIG. 2B, various portions of afabrication process to form strings of memory cells or other electronicdevices, are shown according to an embodiment. The NAND memory devicestructure 200 of FIG. 2A and FIG. 2B is similar to the NAND memorydevice 100 of FIG. 1A through FIG. 1H. However, the etch stop 105A (FIG.1A) comprising, for example, a high-κ dielectric material, may no longerbe required as an etch stop for formation of the pillar opening 110(FIG. 1B). As indicated above, the etch stop 105A of FIG. 1A allows thepillar opening 110 to be formed in a single step.

Instead of the etch stop 105A, a source material 201 is selected toinclude a transition metal that may be combined with a semiconductormaterial, forming, for example, an inorganic compound. In a specificexemplary embodiment, tungsten disilicide (WSi₂), or more generally,tungsten silicide (WSi_(x)) may be formed for the source material 201from, for example, using source gases of tungsten hexafluoride (WF₆) andmonosilane (SiH₄) or dichlorosilane (H₂SiCl₂) in a chemical vapordeposition (CVD) process. The resulting WSi_(x) film may subsequently beannealed to form a more conductive, stoichiometric form. In thisexample, the WSi_(x) film used to form the source material 201 is arelatively hard material and thus forms an etch stop.

FIG. 2B shows the channel-fill material 133 added to the NAND memorystructure 200. As with the NAND memory device 100 of FIG. 1H, aresulting cell pillar formed from the channel-fill material 133 iscontinuous from the semiconductor material 115 to the source material201 (or the source material 101 in FIG. 1H). In a specific exemplaryembodiment where NAND memory devices are formed using the disclosedsubject matter, the cell pillar is continuous and formed in asingle-process operation from the SGD to the source.

FIG. 3 is a block diagram of a system 300 with a memory device that mayinclude one or more of the various embodiments described herein. Thesystem 300 is shown to include a controller 303, an input/output (I/O)device 311 (e.g., a keypad, a touchscreen, or a display), a memorydevice 309, a wireless interface 307, a static random access memory(SRAM) device 301, and a shift register 315, each coupled to one anothervia a bus 313. A battery 305 may supply power to the system 300 in oneembodiment. The memory device 309 may include a NAND memory, a flashmemory, a NOR memory, a combination of these, or the like. The memorydevice 309 may include one or more of the novel devices and structuresdescribed herein.

The controller 303 may include, for example, one or moremicroprocessors, digital signal processors, micro-controllers, or thelike. The memory device 309 may be used to store information transmittedto or by the system 300. The memory device 309 may optionally also beused to store information in the form of instructions that are executedby the controller 303 during operation of the system 300 and may be usedto store information in the form of user data either generated,collected, or received by the system 300 (such as image data). Theinstructions may be stored as digital information and the user data, asdisclosed herein, may be stored in one section of the memory as digitalinformation and in another section as analog information. As anotherexample, a given section at one time may be labeled to store digitalinformation and then later may be reallocated and reconfigured to storeanalog information. The controller 303 may include one or more of thenovel devices and structures described herein.

The I/O device 311 may be used to generate information. The system 300may use the wireless interface 307 to transmit and receive informationto and from a wireless communication network with a radio frequency (RF)signal. Examples of the wireless interface 307 may include an antenna,or a wireless transceiver, such as a dipole antenna. However, the scopeof the inventive subject matter is not limited in this respect. Also,the I/O device 311 may deliver a signal reflecting what is stored aseither a digital output (if digital information was stored), or as ananalog output (if analog information was stored). While an example in awireless application is provided above, embodiments of the inventivesubject matter disclosed herein may also be used in non-wirelessapplications as well. The I/O device 311 may include one or more of thenovel devices and structures described herein.

The various illustrations of the procedures and apparatuses are intendedto provide a general understanding of the structure of variousembodiments and are not intended to provide a complete description ofall the elements and features of the apparatuses and methods that mightmake use of the structures, features, and materials described herein.Based upon a reading and understanding of the disclosed subject matterprovided herein, a person of ordinary skill in the art can readilyenvision other combinations and permutations of the various embodiments.The additional combinations and permutations are all within a scope ofthe present invention.

The Abstract of the Disclosure is provided to allow the reader toquickly ascertain the nature of the technical disclosure. The abstractis submitted with the understanding that it will not be used tointerpret or limit the claims. In addition, in the foregoing DetailedDescription, it may be seen that various features are grouped togetherin a single embodiment for the purpose of streamlining the disclosure.This method of disclosure is not to be interpreted as limiting theclaims. Thus, the following claims are hereby incorporated into theDetailed Description, with each claim standing on its own as a separateembodiment.

What is claimed is:
 1. An apparatus, comprising: a source materialincluding a transition metal combined with a semiconductor material; anactive switching device; a memory stack arranged between the sourcematerial and the active switching device and having alternating levelsof conductive materials and dielectric materials such that each level ofconductive material is separated from another level of conductivematerial by a level of dielectric material, at least some of theconductive materials including a recessed charge storage structureformed substantially within a level of respective ones of the conductivematerial and separated from adjacent portions of the dielectric materialby a charge-blocking dielectric material; a buffer material formedbetween a level corresponding to the source material and the memorystack; and a channel-fill material that is continuous from the sourcematerial to a level of the active switching device, the charge storagestructures formed laterally away from the channel-fill material.
 2. Theapparatus of claim 1, wherein each of the recessed charge storagestructures are formed substantially between adjacent ones of thealternating levels of dielectric materials.
 3. The apparatus of claim 1,wherein at least one of the dielectric materials is a solid electrolyte.4. The apparatus of claim 1, wherein at least one of the dielectricmaterials is a chalcogenide.
 5. The apparatus of claim 1, wherein thechannel-fill material forms a cell pillar.
 6. The apparatus of claim 1,wherein the source material comprises tungsten disilicide.
 7. Theapparatus of claim 1, wherein the source material comprises tungstensilicide.
 8. The apparatus of claim 1, further comprising a buffermaterial formed between the level corresponding to the source materialand the memory stack.
 9. The apparatus of claim 1, wherein theconductive material comprises a semiconductor material.
 10. Theapparatus of claim 9, wherein the semiconductor material comprises aconductively-doped polysilicon.
 11. An apparatus, comprising: a sourcematerial including a transition metal combined with a semiconductormaterial; a channel-fill material; and a memory stack having alternatinglevels of conductive materials and dielectric materials such that eachlevel of conductive material is separated from another level ofconductive material by a level of dielectric material, the memory stackincluding multiple recessed charge storage structures formedsubstantially within a level of respective ones of the conductormaterial and laterally away from the channel-fill material andsubstantially between adjacent ones of the alternating levels ofdielectric materials.
 12. The apparatus of claim 11, wherein themultiple recessed charge storage structures are separated from aremaining portion of the conductive material on the same level by adielectric material.
 13. The apparatus of claim 11, wherein thedielectric material is an inter-polysilicon dielectric material and thecharge storage structure includes a charge storage material formed overthe inter-polysilicon dielectric material.
 14. The apparatus of claim13, wherein the inter-polysilicon dielectric material is acharge-blocking dielectric material.
 15. The apparatus of claim 13,wherein the inter-polysilicon dielectric material is a high-dielectricconstant material.
 16. The apparatus of claim 11, wherein a tunnelingmaterial is formed over the charge storage material.
 17. The apparatusof claim 11, further comprising a buffer material formed between a levelcorresponding to the source material and the memory stack; and aswitching device, wherein the memory stack is between the sourcematerial and the switching device.
 18. An apparatus, comprising: asource material including a transition metal combined with asemiconductor material; a memory stack having alternating levels ofsemiconductor materials and dielectric materials, each level of thesemiconductor materials being separated from an adjacent level of thesemiconductor materials by one of the levels of dielectric materials;and multiple recessed charge storage structures formed substantiallybetween adjacent ones of the alternating levels of dielectric materialsand substantially within a level of respective ones of the semiconductormaterial, the multiple recessed charge storage structures formedlaterally away from a channel-fill material, each of the multiplerecessed charge storage structures being separated from adjacentportions of the dielectric material by an inter-polysilicon dielectricmaterial.
 19. The apparatus of claim 18, wherein the source materialcomprises tungsten silicide; and further comprising a switching device,wherein the channel-fill material is continuous from the source materialto a level of the switching device.
 20. The apparatus of claim 18,wherein the memory stack includes conductive-bridging random-accessmemory cells.